JP3645888B2 - Halftone phase shift mask - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a halftone phase shift mask, and more particularly to a technique for accurately manufacturing a halftone phase shift mask.
[0002]
[Prior art]
As the phase shift mask, there is a so-called halftone type phase shift mask represented by Patent Document 1. This halftone type phase shift mask has a feature that the configuration is simple because it has both a function of shifting the phase of exposure light and a function of substantially blocking exposure light in a semi-transparent film pattern. It was. However, in this type of halftone phase shift mask, when repeatedly used as a mask (reticle) of a reduction exposure projection apparatus (stepper), the light transmission area of the covering member (aperture) and the transfer area of the reticle Due to the misalignment and the like, a phenomenon that is substantially the same as that in the region that should not be exposed occurs, and a problem that pattern defects and other disadvantages are likely to occur has occurred.
[0003]
Therefore, a technique for solving this problem has already been filed by the present applicant (see Patent Document 2). The halftone phase shift mask by these techniques further includes a light shielding film pattern mainly composed of chromium in addition to the phase shift film (semi-transparent film) pattern, and even when repeatedly used as a stepper reticle, There was an effect that the region that should not be exposed can be surely shielded by the light shielding film pattern.
[Patent Document 1]
JP-A-4-136854 (pages 7-20, FIG. 1)
[Patent Document 2]
JP-A-6-282063 (page 3-5, FIG. 1)
[0004]
[Problems to be solved by the invention]
By the way, in a halftone phase shift mask of a type having a light shielding film pattern, when etching the light shielding film on the phase shift film, a defect is caused by the fact that the light shielding film remains. .
However, in a conventional inspection apparatus using transmitted light that is generally used for inspection of pattern defects (for example, KLA-Tencor KLA-300 series), a phase shift film (semi-transmissive film) is used as a light shielding film. Since the transmittance is recognized as being approximately 0% in the same manner as in the above, the phase shift film and the light shielding film cannot be distinguished, and it is impossible to detect surplus defects of the light shielding film on the phase shift film. It was.
[0005]
The present invention has been made under the background as described above, and it is an object of the present invention to be able to inspect defects of a light shielding film on a phase shift film of a halftone type phase shift mask, in particular, excess defects.
[0006]
[Means for Solving the Problems]
By the way, as an apparatus that exclusively inspects for the presence or absence of foreign matters such as particles adhering to the mask rather than defects in the pattern itself, an apparatus that performs inspection using at least reflected light from the mask (for example, reflected light and transmitted light) KLA-Tencor's STARlight, etc.) that uses both of them for inspection. The present inventor has found that by controlling the optical characteristics (reflection characteristics) of the halftone phase shift mask, it is possible to inspect defects of the light shielding film on the phase shift mask, particularly surplus defects, by using the above-described apparatus. It came to.
[0007]
That is, according to the first aspect of the present invention, a halftone phase shift mask having a semi-transparent film pattern and a light-shielding film pattern formed on the semi-transparent film pattern is manufactured on a transparent substrate. Manufacturing method of forming a light-shielding film pattern by forming a semi-transparent film pattern on a transparent substrate and etching the light-shielding film on the semi-transparent film pattern in the halftone phase shift mask manufacturing method And a mask inspection step of irradiating the mask formed by the mask manufacturing step with defect inspection light and inspecting the presence or absence of excess defects due to the light shielding film remaining on the semi-transparent film pattern based on the reflected light. And the mask manufacturing process includes a method in which the reflectance of the semi-transmissive film pattern and the light-shielding film pattern with respect to the defect inspection light remains on the semi-transmissive film pattern in the inspection process. Method for producing a halftone phase shift mask, characterized in that to form the respective patterns to indicate the differences that can be detected by distinguishing the surplus defects due to the film from HanToruHikarimaku pattern.
[0008]
The defect referred to here is a portion (excess defect) where a light shielding film pattern (light shielding film) is excessively formed on a semi-transparent film pattern (phase shift film).
The reflectance of the light shielding film pattern or the semi-transparent film pattern can be controlled by the material and film thickness, for example.
[0009]
According to the second aspect of the present invention, the halftone phase shift mask according to the first aspect is configured such that a difference in reflectance of each pattern with respect to the defect inspection light is 5% or more. A halftone phase shift mask is provided.
It is preferable to set the difference in reflectance between the patterns to 10% or more because defects can be detected more reliably.
[0010]
According to the third aspect of the present invention, in the halftone phase shift mask according to the first or second aspect, the reflectance of the light shielding film pattern with respect to the defect inspection light is such that the half of the defect inspection light has the half. A halftone phase shift mask is provided which is configured to be larger than the reflectance of the translucent film pattern.
[0011]
According to the fourth aspect of the present invention, in the halftone phase shift mask according to any one of the first to third aspects, the reflectance of each pattern is 30% for the exposure light. A halftone phase shift mask is provided which is configured as follows.
[0012]
The exposure light referred to here is not only the exposure light irradiated to the halftone phase shift mask, but also the exposure light to the photoresist formed on the blank in the process of manufacturing the halftone phase shift mask. Including.
[0013]
According to the fifth aspect of the present invention, there is also provided a halftone phase shift mask blank used as a material for manufacturing the halftone phase shift mask according to any one of the first to fourth aspects. .
[0015]
【Example】
Hereinafter, a method of manufacturing a halftone phase shift mask according to the embodiment will be described with reference to FIG.
First, a transparent substrate 1 having a length of 6 inches × width of 6 inches × thickness of 0.25 inch was obtained by mirror-polishing a quartz substrate and performing predetermined cleaning.
Next, using a mixed target of molybdenum (Mo) and silicon (Si) (Mo: Si = 20: 80 mol%), a mixed gas atmosphere of Ar (Ar) and nitrogen (N ₂ ) (Ar: 10%, N ₂ : 90%, pressure 0.3 Pa), reactive sputtering was performed to form a MoSiN semitranslucent film 2 having a film thickness of 100 nm on the transparent substrate 1.
[0016]
Next, the light-shielding film 3 was formed on the semi-transparent film 2 using an in-line sputtering apparatus in which a plurality of chromium (Cr) targets were disposed in the same chamber.
Specifically, first, reactive sputtering is performed in a mixed gas atmosphere of argon (Ar) and nitrogen (N ₂ ) (Ar: 72% by volume, N2: 28% by volume, pressure 0.3 [Pa]). As a result, a CrN film having a film thickness of 20 nm was formed on the transparent substrate 1.
Subsequently, reactive sputtering is performed in a mixed gas atmosphere of argon (Ar) and methane (CH ₄ ) (Ar: 96.5% by volume, CH ₄ : 3.5% by volume, pressure 0.3 [Pa]). As a result, a CrC film having a thickness of 37 [nm] was formed on the CrN film.
Subsequently, reactive sputtering is performed in a mixed gas atmosphere of argon (Ar) and nitric oxide (NO) (Ar: 87.5% by volume, NO: 12.5% by volume, pressure 0.3 [Pa]). As a result, a CrON film having a film thickness of 15 nm was formed on the CrN film.
The CrON film exhibits an antireflection function, and the reflectance of the light shielding film 3 can be controlled by controlling the film thickness of the CrON film.
[0017]
The above CrN film, CrC film, and CrON film are continuously formed using an in-line sputtering apparatus, and the light shielding film 3 containing these CrN, CrC, and CrON is formed in the thickness direction. On the other hand, the component is continuously changed.
[0018]
Next, a positive electron beam resist (ZEP7000: manufactured by Nippon Zeon Co., Ltd.) 4 was applied on the light-shielding film 3 by spin coating so as to have a film thickness of 500 [nm] (see FIG. 1A).
Next, a desired pattern was drawn on the positive electron beam resist 4 by MEBES manufactured by ETEC and developed to form a first resist pattern 41 (see FIG. 1B).
Next, by using the first resist pattern 41 as a mask, the light shielding film 3 was patterned by dry etching using chlorine and oxygen to form a first light shielding film pattern 31 (see FIG. 1C).
[0019]
Next, using the first resist pattern 41 and the first light-shielding film pattern 31 as a mask, the semi-transparent film 2 is dried using a mixed gas of CF ₄ / O ₂ under conditions of pressure: 0.4 Torr and RF power: 100 W. Etching was performed to form a translucent film pattern 21 (FIG. 1D).
Next, the first resist pattern 41 was removed, and a halftone phase shift mask patterned to the first stage was completed (see FIG. 1E).
[0020]
Next, a photoresist (AZ1350: manufactured by Clariant) 5 was applied by a spin coating method to a thickness of 500 [nm] and baked (FIG. 1 (f)).
Next, a program defect that becomes an excessive light-shielding film pattern was superimposed and exposed with an ALTA 3000 manufactured by ETEC, and developed to form a second resist pattern 51 (see FIG. 1G).
Next, using the second resist pattern 51 as a mask, the first light-shielding film pattern 31 is etched using an etchant composed of ceric ammonium nitrate and perchloric acid to complete the second light-shielding film pattern 311 (FIG. 1 (h)).
Next, the second resist pattern 51 was peeled off, and then predetermined cleaning was performed to obtain the halftone phase shift mask 10.
[0021]
Then, the obtained half-tone phase shift mask 10 was irradiated with light, and the optical characteristics of the semi-transparent film pattern 21 and the second light-shielding film pattern 311 were measured. The measurement results are shown in FIG. In the figure, the vertical axis represents the reflectance (%), and the horizontal axis represents the wavelength [nm] of the irradiation light. Reference symbol A indicates the relationship between the wavelength of the irradiation light and the reflectance of the semi-transparent film pattern 21 (or the semi-transparent film 2, hereinafter the same), and reference symbol B indicates the wavelength of the irradiation light and the second light shielding. It is a graph which shows the relationship with the reflectance of the film | membrane pattern 311 (or light-shielding film 3, and the following is same).
[0022]
From FIG. 2, the reflectance of the second light-shielding film pattern 311 is higher at the defect inspection wavelength (eg, 488 [nm]) than at the exposure wavelength (eg, 248 [nm]). It can be seen that it is configured to be higher.
[0023]
Further, as can be seen from the figure, this half-tone phase shift mask 10 has a first difference in which the difference in reflectance between the semi-transparent film pattern 21 and the second light-shielding film pattern 311 is 5% or more. The wavelength range is configured to exist.
If the difference in reflectance between the patterns is 5% or more, the difference in contrast between the patterns can be greatly increased in a defect inspection apparatus that performs defect inspection based at least on the reflected light from the mask. Therefore, even a minute defect can be reliably detected.
[0024]
The first wavelength region is a region having a wavelength of about 350 [nm] or more. Accordingly, in this case, light having a wavelength of 350 [nm] or more can be used as the defect inspection light.
Further, in the first wavelength range, in the range of approximately 400 [nm] or more, the difference in reflectance between the patterns is 20% or more.
In particular, when the wavelength of the irradiation light is 488 [nm], the reflectance of the second light-shielding film pattern 311 is more than twice the reflectance of the semi-transparent film pattern 21, and the defect inspection light In this case, it is preferable to use light having a wavelength of 488 [nm].
[0025]
As can be seen from the figure, in the half-tone phase shift mask 10, the second light-shielding film pattern 311 has a higher reflectance than the semi-transparent film pattern 21 in the first wavelength region. This is particularly suitable for inspection of surplus defects such as chromium residue.
[0026]
As shown in the figure, the halftone phase shift mask 10 has a second wavelength at which the reflectances of the semi-transparent film pattern 21 and the second light-shielding film pattern 311 are both 30% or less. It is configured so that there are more areas.
If the reflectance of each pattern is 30% or less, the generation of stray light with respect to the exposure light is prevented, so that not only the accuracy of the transfer pattern can be improved, but also the dimensional accuracy of the halftone phase shift mask 10 itself can be improved. Become. Even when this halftone phase shift mask 10 is used as a reticle, adverse effects due to irregular reflection of light during exposure by a stepper can be suppressed.
[0027]
The exposure light referred to here is not only exposure light used when pattern transfer is performed using the halftone phase shift mask 10 but also exposure light used for electron beam drawing on the positive electron beam resist 4 described above. Is also included.
[0028]
The second wavelength region is a region of 365 [nm] or less. Therefore, in this case, as the exposure light, i-line having a wavelength of 365 [nm] and light having a shorter wavelength can be used.
In particular, when the wavelength of the irradiation light is 248 [nm], the reflectance of the second light-shielding film pattern 311 and the semi-transparent film pattern 21 is both about 20 [%], and the exposure light It is preferable to use light with a wavelength of 248 [nm] (KrF laser).
[0029]
[Comparative example]
For comparison, an in-line sputtering apparatus in which a plurality of chromium (Cr) targets are arranged in the same chamber is used, and CrN is a mixed gas atmosphere of argon (Ar) and nitrogen (N ₂ ) (Ar: 80% by volume) , N ₂ : 20 vol%, pressure 0.3 [Pa]), CrC is a mixed gas atmosphere of Ar (Ar), methane (CH ₄ ) and helium (He) (Ar: 30 vol%, CH ₄ : 10 vol%, He: 60 vol%, pressure 0.3 [Pa]), CrON is a mixed gas atmosphere of argon (Ar) and nitric oxide (NO) (Ar: 80 vol%, NO: 120) A light-shielding film made of CrN, CrC, and CrON was formed on the semi-transparent film on the transparent substrate by performing reactive sputtering respectively in volume% and pressure 0.3 [Pa]. By adjusting the sputtering power during the film formation process, the CrN film thickness was set to 15 [nm], the CrC film thickness was set to 60 [nm], and the CrON film thickness was set to 25 [nm]. .
The other steps were the same as in the above-described example, and a halftone phase shift mask was obtained.
[0030]
The resulting half-tone phase shift mask was irradiated with light, and the reflectance of the light shielding film pattern according to the comparative example was measured. In FIG. 2, the symbol C is a graph showing the relationship between the wavelength [nm] of irradiated light and the reflectance of the light shielding film pattern according to the comparative example.
As shown in the figure, the light-shielding film pattern according to the comparative example exhibits a good low reflection function in the same manner as the semi-transparent film pattern over a wavelength range of 200 [nm] to 800 [nm]. In the region, there is no place where the reflectivity is sufficiently higher than that of the semi-transparent film pattern, and it has been found that there is a concern that the defect of the light shielding film pattern cannot be reliably detected in the defect inspection.
In particular, at the inspection wavelength (488 [nm]), although the reflectance of the light shielding film pattern according to the comparative example exceeds the reflectance of the semi-transparent film pattern, the difference is several percent. Has been found by the inventor's research that defects cannot be sufficiently detected in a defect inspection apparatus.
[0031]
In addition, each structure, conditions, etc. which were employ | adopted by the present Example are examples, and it can change a design suitably in the range which does not deviate from the meaning of this invention.
For example, the wavelengths of the exposure light and the defect inspection light described above are not particularly limited. Further, the material of the light shielding film pattern and the semi-transparent film pattern is not particularly limited to the examples. The reflectance of the light shielding film pattern or the semi-transparent film pattern can be controlled by the film thickness, but the reflectance can also be controlled by the material.
In addition, as long as the difference in reflectance of each pattern with respect to the defect inspection light is 5% or more, the halftone phase shift mask is not limited to which pattern shows higher reflectance with respect to the defect inspection light. . Accordingly, the semi-transparent film pattern may be configured to have a higher reflectance than the light shielding film pattern with respect to the defect inspection light.
[0032]
In the case of a single layer, the semi-transparent film can be mainly composed of metal, silicon, oxygen and / or nitrogen. In addition to nitrided molybdenum and silicon (MoSiN-based material), for example, oxidation Molybdenum and silicon (MoSiO-based material), oxidized and nitrided molybdenum and silicon (MoSiON-based material), oxidized tantalum and silicon (TaSiO-based material), nitrided tantalum and silicon (TaSiN-based material), oxidized And nitrided tantalum and silicon (TaSiON-based material), oxidized tungsten and silicon (WSiO-based material), nitrided tungsten and silicon (WSiN-based material), oxidized and nitrided tungsten and silicon (WSiON-based material) , Oxidized titanium and silicon (TiSiO series) Material), nitrided titanium and silicon (TiSiN material), oxidized and nitrided titanium and silicon (TiSiON material), oxidized chromium and silicon (CrSiO material), nitrided chromium and silicon (CrSiN material) Material), oxidized and nitrided chromium and silicon (CrSiON-based material), fluorinated chromium and silicon (CrSiF-based material), and the like. Furthermore, these substances are generally represented by carbon, hydrogen, fluorine, helium or other conventional compounds as these compounds or compounds with these substances as long as the function as a halftone material film is not impaired. An appropriate amount of the substance may be included.
[0033]
In the present invention, for example, molybdenum silicide oxide, molybdenum silicide nitride, molybdenum silicide oxynitride, tantalum silicide oxide, tantalum silicide nitride, tantalum silicide oxynitride, tungsten silicide oxidation Tungsten silicide nitride, tungsten silicide oxynitride, titanium silicide oxide, titanium silicide nitride, titanium silicide oxynitride, or one or more of these materials and silicon nitride and / or metal nitride Substances such as mixtures with substances can also be used as the material constituting the halftone material film. The halftone material film may be a laminated film of two or more layers.
[0034]
【The invention's effect】
According to the present invention, it is possible to inspect for defects of the light shielding film on the phase shift film of the halftone phase shift mask, in particular, excess defects. Further, according to the present invention, even a minute defect of the halftone phase shift mask can be reliably detected. In addition, according to the present invention, defect inspection of a halftone phase shift mask can be performed more strictly and easily using an automatic defect inspection apparatus. As a result, it becomes possible to provide a halftone phase shift mask with an unstable yield.
[Brief description of the drawings]
FIG. 1 is a view for explaining a method of manufacturing a halftone phase shift mask according to an embodiment.
FIG. 2 is a diagram showing optical characteristics of a halftone phase shift mask according to an embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Transparent substrate 21 Semi-transmissive film pattern 311 2nd light shielding film pattern (light shielding film pattern)
10 Halftone phase shift mask

Claims (4)

In a halftone phase shift mask manufacturing method for manufacturing a halftone phase shift mask having a semitransparent film pattern and a light shielding film pattern formed on the semitransparent film pattern on a transparent substrate,
A mask manufacturing step of forming a light-transmitting film pattern by forming a light-transmitting film pattern on the transparent substrate and etching the light-shielding film on the semi-transparent film pattern;
A mask inspection step of irradiating the mask formed by the mask manufacturing step with defect inspection light and inspecting the presence or absence of excess defects due to the light shielding film remaining on the semi-transparent film pattern based on the reflected light. ,
In the mask manufacturing process, the semi-transparent film has a reflectivity of the semi-transmissive film pattern and the light-shielding film pattern with respect to the defect inspection light, and surplus defects due to the light-shielding film remaining on the semi-transmissive film pattern in the inspection process. A method of manufacturing a halftone phase shift mask, wherein each pattern is formed so as to show a difference that can be detected separately from the pattern. 2. The method of manufacturing a halftone phase shift mask according to claim 1, wherein a difference in reflectance of each pattern with respect to the defect inspection light is 5% or more . The reflectance of the said light shielding film pattern with respect to the said defect inspection light is comprised so that it may become larger than the reflectance of the said semi-transparent film pattern with respect to the said defect inspection light. Method for manufacturing halftone phase shift mask. 4. The halftone phase shift mask according to claim 1, wherein the reflectance of each of the patterns is 30% or less with respect to exposure light. 5. Production method.

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